Avoid the autumn chill

When someone with a cold on a Tube carriage sneezes, the droplets that shoot out of their mouth and nose at speeds of up to 100mph contain 100,000 virus cells. These are carried across the carriage and are inhaled by unsuspecting commuters or land on a handrail for the next person to pick up.

It's no wonder London is a breeding ground for viruses. We commute in packed trains and buses, work in airconditioned offices and unwind in busy bars - viruses thrive and spread rapidly. And if you've been on public transport you can hardly not notice the coughs, sneezes and splutters of your fellow commuters - yes, the cold and flu season is upon us.

"I would say London is the cold capital of the UK," says Professor Ron Eccles, director of the Common Cold Centre at Cardiff University. "That's due to the density of the population and because life is more stressful from the pressures of getting to and from work."

A sneeze expels large and tiny particles, the large fall to the ground very quickly and don't go far, but the smallest will take more than four hours to drop a distance of two metres, which means someone who sneezed and has long since left the carriage may be to blame for your cold next week.

"The other way viruses are transmitted is through dirty fingers," says Professor Eccles. "Someone with a cold pokes around in their nose, gets their fingers contaminated and then touches surfaces like door handles or vending machines."

Don't you just love your fellow city dwellers? But short of living in a sealed bubble, how can you minimise the chances of infection? We show you what to do and pinpoint the most risky areas in London:

At home

The problem: This is where most bugs lurk. Close contact gives cold viruses many opportunities to spread, says Professor Eccles. "Your body space is limited and we tend to do things like cuddle up on the sofa. The other reason is the exposure is far more long term because most of us will spend at least eight to 12 hours at home in one go. Children are the best carriers because their dirty habits can spread a lot of viruses."

The solution: Try to avoid kissing or sharing drinks with family members who have colds, as this is a great way for them to spread. Teach children to cover their mouths when they cough or sneeze, and wash hands regularly.

In the office

The problem: Sneezing colleagues can be a risk but unless your office breaks health-and-safety regulations on space, the risk of inhaling infected droplets is quite small. A bigger worry is contaminated surfaces, especially where staff congregate, such as the drinks machine and the photocopier. Air conditioning can be a problem as well, says Professor Eccles: "Not because it spreads viruses, but because it dries the lining of the nose, which is the first defence against infection."

The solution: If you have a cold, wash your hands - it will cut down transmission. And if the air conditioning is leaving your throat and nose dry, get your employer to adjust the humidity.

In a restaurant

The problem: Depending on the level of hygiene, contaminated surfaces could pose a problem.

The solution: Order dishes loaded with garlic or chilli - garlic because it has disease-fighting properties, chilli as it helps clear out the sinuses.

On the Tube

The problem: It's virtually impossible to escape the transmission of infected droplets during rush hour. In Tokyo, things are so bad some people wear face masks to protect themselves. "The more crowded the train the higher the risk," says Professor Eccles. "But the duration of exposure is important, too. If you have a long journey then you're more likely to catch a cold." Changes in temperature - such as when you leave the street for a stuffy train - are also factors.

The solution: Once on the Tube, take your coat off, then wrap up again when you get off. As for masks? Okay if you have a cold and want to protect others, says Professor Eccles, but not much good at stopping infection. "The virus gets transmitted to the eyes, also," he adds, "so you would need to wear goggles to stop it."

On the bus

The problem: As bus journeys probably take longer than Tube trips this can increases the duration of exposure. The flu virus can survive for up to 48 hours on non-porous surfaces such as handlebars and rails.

The solution: Your proximity to infected passengers is the key, so try to get a seat away from standing areas. When infected, you can be contagious for up to one day before your symptoms appear and up to a week afterwards. Use hankies and wash your hands regularly.

At a nightclub

The problem: Late nights and excess alcohol put the body's immune system under stress, which means it's not as good at fighting off invading viruses.

The solution: Don't overdo it. Give your body a chance to recover from a heavy night out before you embark on another one.

The Government is encouraging everyone over 65 to have the flu vaccine. For details, contact your GP.